Ingredient review
PEI-35
INCI: PEI-35
PEI-35 is a synthetic polymer that helps products spread evenly and stay put, but it's not a star ingredient for skin health.
In plain English
PEI-35 is a man-made ingredient that helps cosmetic products form a thin, even film on your skin or hair. Think of it like a gentle glue that helps makeup or hair products stay in place without feeling heavy or sticky. It's not a moisturizer or active treatment, just a helper ingredient for texture and wear.
Review score
Safety, usefulness, and evidence
Potentially useful with some tradeoffs
The evidence base is useful, but some claims depend heavily on the formula.
Risk flags are low for most users, though the finished product can still irritate.
- Source
- synthetic
- Evidence
- moderate
- Irritation
- low
- Clogging risk
- low
Quick decision guide
Useful, but context matters
PEI-35 is generally a lower-concern ingredient when the full formula suits your skin.
Plain-English read
Treat this as a practical screening step before you compare products that contain this ingredient.
- Step 1Start with the score, then check the irritation and clogging risk before judging PEI-35.
- Step 2Use the "Best for" and "Use caution if" sections to match the ingredient to your skin, not just to a marketing claim.
- Step 3If a product stings, breaks you out, or worsens irritation, judge the finished formula and stop using it even if the ingredient scores well.
Score terms in plain English
Irritation risk
lowLess likely to sting, burn, or bother most users, though sensitive skin can still react.
Clogging risk
lowLess likely to feel heavy or contribute to clogged pores for most skin types.
Evidence level
moderateThere is useful support, but formula details and claim strength still matter.
What it is
PEI-35 is a synthetic polymer derived from ethyleneimine. In cosmetics, it's used to improve the feel and performance of products by forming a flexible film on the skin or hair.
How it works
When applied, PEI-35 spreads into a thin, even layer that dries to a flexible film. This film helps other ingredients stay put, reduces flaking, and can give hair products a light hold without stiffness.
Pros
Improves wear time
Helps mascara, eyeliner, and styling products stay in place longer without smudging or flaking.
Lightweight feel
Forms a thin, flexible film that doesn't feel heavy or tacky on skin or hair.
Cons and cautions
Synthetic origin
Not a natural ingredient, which may be a drawback for those seeking plant-based or minimal-ingredient routines.
Limited skin benefit
Does not moisturize, soothe, or treat skin conditions; purely a texture and wear enhancer.
Best for
- Anyone looking for longer-lasting makeup or hair styling
- People who want a lightweight, non-sticky film former
Use caution if
- Those who strictly avoid synthetic ingredients
- People with known sensitivity to polyethylenimine derivatives (rare)
Usage tips
Safety summary
PEI-35 is considered safe for cosmetic use at typical concentrations. It has low irritation and comedogenic potential. However, long-term studies on skin absorption and accumulation are limited.
Research notes
Research on PEI-35 in cosmetics is sparse. Most safety data comes from general polymer toxicology and industry assessments. No major safety concerns have been raised by regulatory bodies.
Common label clues
- Typical concentration
- Typically used at 0.1% to 2%
- Regulatory status
- Approved for use in cosmetics in the US, EU, and many other regions. No specific restrictions beyond general cosmetic safety requirements.
- Common uses
- Hair styling products, Mascara, Eyeliner
- Environmental note
- As a synthetic polymer, PEI-35 may not be biodegradable. Its environmental impact depends on formulation and disposal.
Good to know
- PEI-35 is often found in waterproof or long-wear makeup formulas.
- It is not a common allergen, but any new ingredient should be patch tested if you have reactive skin.
Common questions
What is PEI-35 in beauty products?
PEI-35 is a man-made ingredient that helps cosmetic products form a thin, even film on your skin or hair. Think of it like a gentle glue that helps makeup or hair products stay in place without feeling heavy or sticky. It's not a moisturizer or active treatment, just a helper ingredient for texture and wear.
What does PEI-35 do in a beauty product?
When applied, PEI-35 spreads into a thin, even layer that dries to a flexible film. This film helps other ingredients stay put, reduces flaking, and can give hair products a light hold without stiffness.
Is PEI-35 safe for most people?
PEI-35 is considered safe for cosmetic use at typical concentrations. It has low irritation and comedogenic potential. However, long-term studies on skin absorption and accumulation are limited.
Who should be careful with PEI-35?
Those who strictly avoid synthetic ingredients People with known sensitivity to polyethylenimine derivatives (rare)
Research sources
Ingredient reviews are educational and are not medical advice. Patch test new products and ask a licensed clinician about persistent irritation, allergies, pregnancy-specific questions, or diagnosed skin conditions.